1. Field of the Disclosure
The present disclosure relates to a high-frequency amplifier module including a semiconductor substrate and an insulating substrate on which the semiconductor substrate is mounted. The semiconductor substrate has high-frequency amplifiers amplifying a high frequency signal.
2. Description of the Related Art
Heretofore, various high-frequency amplifiers have become commercially practical. Some high-frequency amplifiers are used in power amplifiers amplifying transmission signals. For example, a high-frequency power amplifier described in Japanese Unexamined Patent Application Publication No. 2001-57511 is used in such a power amplifier.
The high-frequency power amplifier described in Japanese Unexamined Patent Application Publication No. 2001-57511 includes a heterojunction bipolar transistor (HBT) for amplifying a high frequency signal. The base of the HBT for amplifying a high frequency signal is coupled to a high-frequency signal input terminal through an input matching circuit. The collector of the HBT for amplifying a high frequency signal is coupled to a high-frequency signal output terminal through an output matching circuit. The emitter of the HBT for amplifying a high frequency signal is grounded through an inductor. A base bias is applied to the base of the HBT for amplifying a high frequency signal, and a drive voltage is applied to the collector. The linearity of the HBT for amplifying a high frequency signal is improved by grounding the emitter through the inductor.
However, an HBT for amplifying a high frequency signal which operates with a high amplification factor so as to output a desired high signal level may go beyond the range in which the linearity is possibly improved by using an inductor, resulting in a problem such as the occurrence of distortion harmonics.
Amplification to a high signal level causes an HBT for amplifying a high frequency signal to be heated. Thus, the amplifying characteristics of the HBT for amplifying a high frequency signal may be degraded, resulting in a problem such as the occurrence of distortion harmonics.